Recent increases in public concern for the environment have resulted in various government imposed environment regulations. Among such regulations are requirements relating to the monitoring of groundwater quality. In response to these requirements, water quality analytic capabilities have been improved and water sampling equipment has been developed. Much of the previously developed sampling equipment has not been effective, however, in obtaining consistent, non-contaminated water samples that are accurately representative of the water system from which the sample is taken.
The inadequacies of the previous sampling equipment stem largely from such causes as cross-contamination between sampling sites, ineffective and inconsistent field cleaning methods, contamination due to equipment handling, and inconsistent well depth sampling. In addition to presenting sample quality problems, much of the previous equipment has been heavy and bulky and thus difficult to transport from one monitoring site to another. Another problem associated with the previous sampling equipment is the amount of time it takes to obtain an acceptable sample. Prior to accepting a sample, the well must be purged 3 to 5 times. Depending on the size of the well, the depth of the groundwater in the well and the size of the pump, an excessive amount of time can be required to obtain an acceptable groundwater sample. Finally, much of such previous equipment has proved to be complicated to operate, inordinately expensive, and impractical for sampling at remote locations where site access is severely limited.
In accordance with the present invention, a fluid sampling apparatus is provided for use in obtaining accurate samples of groundwater or other fluids. In the preferred embodiment, the pump is dedicated to a particular monitoring well or other sampling site in order to substantially avoid cross-contamination of samples from site to site and is constructed from light weight non-contaminating materials. A packer, associated with the pump, is provided for the fluid sample apparatus which minimizes the amount of liquid which must be pumped to purge the well prior to obtaining an acceptable sample.
A fluid sampling pump for use in conjunction with the present invention to which a packer is added to reduce the amount of liquid which must be purged prior to sampling is disclosed in U.S. Pat. No. 4,489,779 issued Dec. 25, 1984 to Dickinson et al. and U.S. Pat. No. 4,585,060 issued Apr. 29, 1986 to Bernardin et al. The disclosures of which are hereby incorporated by reference.
The preferred sampling pump is a submersible, fluid actuated pump wherein the actuating fluid is preferably a gas. A first flexible bladder member separates and isolates the interior of the pump into two chambers; a first chamber that contains the sample fluid and is in communication with both the pump inlet and outlet and a second chamber that surrounds the first chamber with the first bladder disposed therebetween. The second chamber is connected to a source of actuating gas. A second flexible bladder member, or packer, forms a third chamber that surrounds the second chamber with the outside wall of the pump disposed therebetween. The third chamber is also connected to a source of actuating gas. The sample liquid is conveyed through the pump by first pressurizing the third chamber to expand the second bladder member. This separates the groundwater within the monitoring well or other sampling site into two regions, with the region below the second bladder member being in communication with the first chamber of the pump. The pump is then actuated by alternately pressurizing and venting or relieving the pressure in the second chamber of the pump to contract and relax the first bladder member thus alternately decreasing and increasing the volume of the first chamber. Sample fluid is drawn into the first chamber from the region below the second bladder member during such increases in volume under the influence of the natural hydrostatic head of the groundwater and is discharged through the pump outlet during such decrease in volume, thereby conveying the sample fluid through the pump. The second bladder member thus minimizes the amount of groundwater which must be pumped in order to purge the well prior to accepting a sample. This is accomplished by isolating the intake to the first chamber from the total volume of fluid in the monitoring well or other sampling site. The components of the pump and packer are preferably composed of low cost, light weight synthetic materials that are non-corrosive and do not otherwise affect the chemical composition of the sampled fluid.
The sampling pump with the integral packer is preferably dedicated to, and thus remains in, a particular sampling site or well without fluid pressure supplied to either the second or third chamber. The sampling site or well is substantially isolated from the above-ground surroundings by a wellhead assembly in order to reduce potential contamination during sampling. A portable controller apparatus is provided with quick-disconnect means and includes means for pressurizing the third chamber and means for alternately pressurizing and de-pressurizing the actuating fluid in the second chamber. The fluid sampling apparatus may also optionally include means for measuring the standing level of the fluid in the well.
Additional advantages and features of the present invention will become apparent from the following description and the appended claims taken in conjunction with the accompanying drawings.